PERIODIC STEP-BUNCHING ON A MISCUT PT(111) SURFACE

The temperature dependence of the equilibrium surface morphology of a stepped Pt(111) surface, miscut by 1.8 degrees towards [($) over bar 1 ($) over bar 12], has been studied by X-ray scattering techniques bet ween 300 and 1900 K. Below T-c = 1389 K, the surface is found to be un iformly stepped and unreconstructed. Above T-c, the surface transforms into a periodic array of wide terraces and narrow terraces. Unlike ma croscopic facets, the wide terraces are mesoscopic in extent, ranging from 230 Angstrom at 1389 K to 94 Angstrom at 1900 K. Reflectivity mea surements suggest that multiple-height steps are not prevalent. The wa ve vector characterizing the array (delta) follows a power law versus reduced temperature [t = (T - T-c)/T-c]: delta = delta>(0)t(beta) with beta = 0.66 +/- 0.05.